1. Field of the Invention
This invention relates to new polyisocyanate compositions which contain particular tertiary amines in addition to a polyisocyanate component and to their use as starting materials for the production of polyisocyanate polyaddition products, preferably polyurethane plastics.
2. Description of the Prior Art
Catalysis of the isocyanate addition reaction is of great importance in industrial polyurethane chemistry. The following is a survey of the literature relating to the catalysts conventionally used and their mode of action: A. Farkas and G. A. Mills, Advanced Catalysis, 13.393 (1962); J. H. Saunders and K. C. Frisch, Polyurethanes, Part I, Wiley Interscience, New York, 1962, Chapter VI and K. C. Frisch and L. P. Rumao, J. Macromol, Sci. Revs. Macromol. Chem. (5/1), 103-150 (1970).
The use of polyisocyanates and polyisocyanate compositions, in particular polyurethane prepolymers containing free isocyanate groups, as adhesives has also been known for a long time and is also recorded in the literature: M. Dollhausen, W. Warrach, Polyurethane Adhesives Technology, Adhesives Age, June 1982, page 28; R. Jordan, Polyurethane als Klebstoffe, Seifen Ole, Fette, Wachse, 109 (1983), No. 11/12, pages 333-336; B. Kujawa-Penczek, P. Penczek, Polyurethan-Klebstoffe, Fortschritte in den 80er Jahren, Adhasion 28 (1984) No. 3, pages 7-12. In addition, prepolymers containing free isocyanate groups may be used as binders for air drying coating compositions, i.e. coating compositions which can be hardened by atmospheric moisture (see, for example, Becker/Braun "Kunststoff-Handbuch", Volume 7, Carl Hanser Verlag Munich/Vienna (1983), pages 545 et seq).
The open time of adhesives based on such isocyanate prepolymers and the pot life and drying speed of the corresponding coating compositions depend primarily on the isocyanate group content of the prepolymers and the reactivity of the isocyanate groups. It has frequently been attempted to adjust these properties by the addition of a catalyst but this may cause problems in storage stability.
When polyurethane prepolymers containing free isocyanate groups are kept in storage, they can undergo discoloration, uncontrolled changes in viscosity and the formation of solid particles, especially when light, atmospheric oxygen and moisture are not completely excluded. These undesirable side reactions, which frequently render the products unusable after a certain time in storage, may be accelerated or in many cases caused by the catalysts conventionally used.
It is therefore an object of the present invention to provide new polyisocyanate compositions containing a catalyst which while capable of adjusting the reactivity of the preparations as desired, has a less deleterious effect on the storage stability of the compositions than the catalysts hitherto used.
This problem may be solved by providing the compositions according to the invention described below. The compositions according to the invention are characterized by the presence of certain aminic catalysts of a type defined in more detail below. It was surprising to find that these special amines were particularly suitable for solving the given problem since one would have expected the catalysts according to the invention to behave like amine-initiated polyether polyols, i.e. polyether polyols containing tertiary amino groups. In this case the stability in storage of compositions containing the catalysts according to the invention would be expected to be similar to that of isocyanate prepolymers based on polyether polyols containing tertiary nitrogen atoms. This is surprisingly found not to be the case and the compositions according to the invention have a much greater stability in storage than corresponding compositions based on the aforesaid polyether polyols containing tertiary nitrogen.